Regional anesthesia catheters are hollow body flexible catheters that are designed to be placed next to a nerve or nerve plexus of the human body, and kept in place for up to a few days. Liquid medicine is injected into proximal end of the catheter. The medication then exits from distal end of the catheter and is deposited around the nerve that is intended to be anesthetized. The dispersal of medication around the nerve causes the area innervated by that nerve to become anesthetized. In current anesthesia practice, hollow shaft metal needles are used to place such catheters into position.
Such needles are covered with an electrically insulating covering over the outer surface of most of their length, except the tip and proximal end. An electric impulse sent to the needle is conveyed axially down to the tip of the needle and not radially to surrounding tissues. This allows for more precise placement of the needle tip. A stimulating wire is attached to the proximal end of the needle and is used to connect the needle to an electric supply source or so-called a nerve stimulator device. The distal end of the needle is placed through the skin of the patient and is advanced toward the target nerve. The amount of electric impulse that is sent toward the needle tip is gradually decreased as the needle advances into the patient's body, which helps to localize the target nerve. A muscle contraction at a specific low current verifies the proximity of the needle tip to that nerve. Next, the catheter is placed through needle.
Needles and catheters come in different gauges and lengths, and it is imperative to use catheters with matching needles. Catheters are either stimulating or non-stimulating. Non-stimulating catheters are composed of an elongated hollow body and generally are similar to epidural catheters. Stimulating catheters generally have a hollow body and means for conveying electric current from the proximal end of the catheter to its distal tip. Only a small portion of the distal and proximal ends of the catheter are electrically exposed, while the body is electrically nonconductive. This allows for precise placement of catheter tip next to a nerve.
These days some practitioners use ultrasound devices to visualize the target nerve and place the needle tip, followed by the catheter tip, next to the target nerve. Practitioners may choose to perform the procedure, using ultrasound alone, or they may employ ultrasound and a nerve stimulator simultaneously. In current practice, however, the majority of practitioners prefer to use nerve stimulators.
Placement of regional anesthesia catheters is done using strict sterile techniques to avoid catheter and needle contamination, and thus patient infection. For example, the skin area were where the needle and catheter will be inserted into the patient is prepped and extensively draped. The long resilient catheter is always prone to contamination from surrounding objects. It is also necessary for the practitioner to wear a mask, hat and sterile gloves and even sterile gown in some instances. An assistant is needed to help open sterile packages, connect and disconnect stimulating wires of needle and catheter to nerve stimulator, and operate the nerve stimulator. The assistant will help utilize the ultrasound device as well, if one is used.